Meeting Abstract
12.7 Thursday, Jan. 3 Rapid changes in corticosterone, corticosteroid binding globulin, and testosterone in response to food availability in the zebra finch LYNN, S.L.*; STAMPLIS, T.B.; WEIDA, N.; The College of Wooster; The College of Wooster; The College of Wooster slynn@wooster.edu
Opportunistically breeding zebra finches modulate reproductive physiology in response to changes in immediate environmental conditions such as food and water availability, rather than in response to long�term cues such as photoperiod. In addition, zebra finches respond to a standardized stressor (handling) with elevated secretion of corticosterone (CORT) and a rapid decrease in corticosteroid binding globulin (CBG). We investigated the role of food availability in altering stress physiology and reproductive physiology and behavior of male zebra finches with several goals in mind. First, we determined if acute food deprivation could stimulate an increase in CORT and decrease in CBG. Second, because recent studies have indicated that CBG may bind testosterone (T) as well as CORT in male birds, we explored whether plasma interactions of CORT, CBG, and T in response to fasting could result in rapid clearance of T from the blood. Finally, we investigated whether food deprivation altered expression of undirected song. After subjecting males to 4, 6, and 10-hr fasts, we collected plasma to measure CORT, CBG, and T. We found that plasma CORT was elevated and T was decreased after all fasting periods compared with samples collected from the same males during non-fasted (control) periods. CBG was lower than control levels only after 10 hrs of fasting. Thus, although individual variability was high, free CORT rapidly increased and T rapidly decreased with fasting. We also found that males sang less when fasted than when fed. Our data demonstrate that acute fasting resulted in rapid changes in plasma levels of CORT, CBG, and T, and also inhibited song. We suggest that this physiological flexibility may relate to the opportunistic breeding strategy of zebra finches.
